1. Field of the Invention
The present invention relates to a motion sensor unit and, more particularly, to a type capable of sensing a successive inclination of a mobile member such as a vehicle body continued for more than a predetermined reference time at any angle greater than a predetermined reference value and producing a detection output representative of the sensed inclination.
Furthermore, the invention relates also to a motion sensor unit capable of sensing any shock given to a mobile member such as a vehicle body at a level greater than a predetermined reference value and producing a detection output representative of the sensed shock.
2. Description of the Prior Art
There is known a motion sensor unit of the type that detects the value of an inclination or jolt of a mobile member such as a vehicle body and, upon increase of the detected value beyond a predetermined level, outputs a switching signal to indicate the excess. Such unit is convenient and effective in the use for preventing theft of a vehicle or the like.
FIGS. 12(A)-(C) and 13(A)-(C) illustrate the structures of conventional motor sensor units known heretofore, wherein a sealed receptacle 12 is housed in a casing 11, and mercury 13 is contained in the receptacle. A pair of electrodes 11a and 11b are attached to the casing 11 and are connected either directly or through a resistor R to a battery BT. The receptacle 12 comprises a tray 12a of a conductive material, a cover 12b composed similarly of a conductive material, and an insulator 12c for electrically isolating the tray and the cover from each other, in which the tray 12a and the cover 12b are connected electrically to the electrodes 11b and 11a respectively via leadwires 14. When a high sensitivity is particularly required in sensing the inclination or shock of a mobile member, the inclination angle .theta. of the insulator 12c is decreased (.theta.=.theta..sub.H) as shown in FIG. 13(A). Meanwhile, when it is desired to reduce the sensitivity, the inclination angle .theta. of the insulator 12c is increased (.theta.=.theta..sub.L &gt;.theta..sub.H) as shown in FIG. 13(A).
In case the motion sensor unit is in a horizontal posture, the mercury 13 is existent on the tray 12a as shown in FIGS. 12(A) and 13(A), whereby no closed electric circuit is formed. However, if the motion sensor unit is so inclined that its angle .theta. exceeds either .theta..sub.H or .theta..sub.L, then the mercury 13 is displaced onto the insulator 12c as shown in FIG. 12(B) or 13(B), thereby forming a closed electric circuit. Accordingly, monitoring the formation of such a closed electric circuit renders it possible to discriminate whether or not the inclination angle of the motion sensor unit has exceeded a predetermined value.
In case any shock given to the motion sensor unit becomes greater than a predetermined value, i.e. when the acceleration .alpha. is in excess of .alpha..sub.H [FIG. 12(B)] or .alpha..sub.L (&gt;.alpha..sub.H) [FIG. 13(B)], then the mercury 13 is displaced onto the insulator 12c to form a closed electric circuit.
In any of the conventional motion sensor units, adjustment of the sensitivity with respect to a shock, jolt or inclination is executed by varying the inclination angle .theta. of the insulator. However, it is impossible therein to attain continuous adjustment of the sensitivity by such technique, and there exists another disadvantage that an individually independent adjustment is not achievable relative to the sensitivity for a shock and that for an inclination or jolt.